When a sewage treatment plant Biofilter Column stopped rotating, SpiralWeld’s remanufacturing experts provided a robust solution, working out of hours to ensure the fastest-possible turnaround.

The Challenge

Biofilter Columns are key to the effective operation of water utility companies’ sewage treatment plants.

Working for a water utility company, our engineering client needed specialist support when a Metasil Biofilter Column stopped rotating.

Entrusting SpiralWeld to resolve the issue as quickly as possible, our initial inspection confirmed the ageing column was in poor condition.

A full clean and vapour blast revealed the clearance between inner shaft and outer column was more than 0.500” instead of 0.012” to 0.020”.

Specific issues included:

  • Destroyed lip seals
  • Worn top roller bearing
  • Significant wear to inner shaft and bearing journal on the outer split ring

Both inner shaft and outer column split ring bearing required building up to reduce the clearance.

The Solution

SpiralWeld’s 30+ years of experience in mission critical component remanufacture for the water industry, allowed us to mitigate risk and working out of normal hours we ensured the quickest possible turnaround without affecting quality.

Whilst weld build-up of both surfaces was initially considered, on further inspection the parent material was discovered to be cast iron, making the welding option too risky.

The inner shaft, however, had a sleeve that was a different material and could be welded.

The SpiralWeld team responded with the following Remanufacture+ process:

  1. Remove inner shaft.
  2. Thorough vapour blast of both inner shaft and outer column.
  3. Pre-machine inner shaft sleeve to clean surface.
  4. Build up inner shaft with several passes of carbon steel.
  5. Add a sleeve extension where original sleeve had worn away using a butt weld to secure to the original sleeve.
  6. Cap off full length of sleeve with an Inconel 625 material to provide much-improved corrosion and wear resistance.
  7. Finish machine inner shaft sleeve to correct diameter to match new lip seals and correct clearance with split ring bore.
  8. Bore out split ring to clean material.
  9. Manufacture a new guide ring from gunmetal.
  10. Fit the new guide ring in place and secure for anti-rotation. Fit new lip seals.
  11. Fit a new top roller bearing.
  12. Re-assemble inner shaft to outer column.
  13. Paint outer column with corrosion-resistant and hard-wearing paint.

A Successful Outcome

SpiralWeld successfully completed the remanufacturing of this Metasil Biofilter Column in just two weeks.

The Biofilter Column was commissioned and working well the day it was returned to the treatment plant.

Client Response

“Just a quick email to say a massive thanks for the Biofilter project – install went exactly to plan and is now fully operational. I’ve certainly had some sleepless nights over it after finding the mess of the previous repairs and some of the setbacks we’ve had!”

For further information on our services, please do not hesitate to contact us.